In a liquid chromatography system, a sample followed by an elution fluid are injected into a separation column. The separation column contains a packing or matrix medium or material, as well known in the art, which interacts with the various components of the sample fluid to be separated. The composition of the separating medium depends on the fluid being directed therethrough so as to produce the desired separation. The separation column generally known in the art are of a cylindrical construction and the fluid flows axially through a separating medium bed (packing or matrix) retained in the column. The medium bed is retained between supports or frits on either or both ends of the column. As the sample and elution fluids pass through the separating medium bed, the constituents of the sample fluid travel at different rates due to their interaction with the matrix or packing material. As a result, these constituents emerge separated (i.e., have different elution times) in the outlet stream of the column.
These prior known approaches are exemplified by the following U.S. Pat. Nos. 3,422,605 issued Jan. 21, 1969, to R. P. Crowley; 3,453,811 issued July 8, 1969, also to R. P. Crowley; 3,780,866 issued Dec. 25, 1973 to L. V. Ek et al; 4,133,562, issued Jan. 9, 1979 to L. H. Andren and 4,354,932 issued Aug. 19, 1982 to R. J. McNeil.
The available matrices or separation material beds for separating substances of large molecular weight are soft and compress easily. Matrix compression in turn causes dramatically reduced flow through the separation column. When chromatographic separation systems are scaled up for commercial purposes, more matrix volume is required and thus larger columns have to be employed. Additionally, the process requires a substantial increase in the fluid flow rate to achieve acceptable production rates. The combination of high flow rates and larger bed height (i.e., hydrostatic head) results in high pressure drops across the matrix that in turn further compress the matrix material, adversely affecting flow through the column. Some prior designs have addressed this problem by incorporating short, wide columns; i.e., columns with large cross-sectional area and reduced height. While this prior design does help reduce pressure drops and improve throughput, the geometry results in large saucer shaped (center dipping) columns when additional scale up is desired. Larger diameter columns have the problems of: (1) inconvenient geometry for fabrication, (2) difficulty in even packing of the column, (3) uneven distribution of the sample over the cross-sectional area, and (4) large dead volume leading to loss in chromatographic resolution. Due to these problems, scale up is often accomplished by using multiple columns in parallel or using larger columns but with smaller diameter-to-height ratios. The first alternative mentioned above can be cumbersome and often results in high costs while the second alternative leads to a recurrence of the problem with compression of the matrix or separator material bed. The process has to be reoptimized since the flow rates have to be altered to reduce pressure drop, leading to considerable expense in terms of time and material. Thus, a need exists in the art for an approach which enables scaling up of chromatographic systems while overcoming the problems enumerated above.
Therefore, it is an object of the present invention to provide a method and apparatus for chromatographic separation which overcomes or significantly reduces prior known problems associated with larger diameter columns, at the same time, lending itself to scale up dimensions.
A further object of the invention is to provide a chromatographic separation system which includes means for reducing the pressure drop across the separation material bed or packing in the direction of flow.
A still further object is to provide a method and apparatus for maintaining an even bed height across the cross-section of a separation material bed of a chromatographic column, while maintaining an even distribution of the sample material across the bed.
Another object of the invention is to provide a chromatographic column which has a geometry for convenient assembly and ease of packing, while enabling a scale-up thereof.
Another object of the invention is to provide a chromatography column utilizing horizontal flow of the sample material through the matrix of the separating medium.
Another object of the invention is to provide a chromatographic column utilizing a cylindrical or cubical construction wherein the flow of the sample material and elution fluid is horizontal (radial flow direction) through the matrix.
Still another object of the invention is to provide an apparatus and method for performing chromatographic separations utilizing horizontal flow through the separating medium bed while maintaining even distribution of the flow and minimal pressure drop across the bed.
Another object of the invention is to provide a chromatographic column having an adjustable bed height.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.